Stumbled on this interesting part from TI recently
TPL5111 solves a typical problem in low power wireless systems- things need to be off most of the time, and wake up periodically to transmit. The usual solution is to pick a microcontroller that can stay asleep in low power mode at a few uA, then wake up on RTC timer. That works most of the time, but sometimes even that is too much standby power. Imagine a system for example that has to work from a small coin cell for 5-10 years. Each uA of sleep current is an 8mAh a year. So in 10 years, 80mAh is wasted. (A typical CR2032 battery for example starts with only 220mAh)
TI’s solution is a timer that can stay on while drawing 35nA. Once set with a single resistor for a particular time interval, between 100ms and 2 hours, it turns power on to the system, waits to hear back from the micro via “done” pin and then turns things back off. TI even provides a handy table of resistor values vs timer settings. Not bad for $0.45@1k, plus there are many other scenarios such an almost zero power scheduler may be handy.
This week’s part is a neat little chip from Texas Instruments. TPS2511 USB Dedicated Charging Port Controller and Current Limiting Power Switch. What this chip is designed to do is handle a bunch of newly developed USB charger handshaking protocols. As many familiar with Adafruit’s Mintyboost and other similar USB chargers for portable devices are aware by now, is that not all devices will charge if you simply give them 5V on a USB connector. Many will expect a particular level on the data lines, like certain i-devices, as documented by LadyAda. And yet others will want data lines to be shorted together to recognize the charger. This chip was designed to handle that automatically and hopefully provide a way to support future devices. Another nice feature is cable drop compensation. With high charging currents, the drop across that 6ft USB cable is no longer negligible. So what this chip does is add a bit of bias current to the feedback pin of a power supply feeding it. By doing that it is raising the output voltage by a predetermined amount to compensate for the drop. This feature activates when a load current exceeds a preset threshold.
TPS2511 typical connection diagram
Very nifty chip- expect a writeup for a project using it soon. But first we must get the boards back from the fab and see if anything smokes!
Today’s post is a small DipTrace library i created for some TI Launchpad Booster Packs I am working on. It is modeled after a similar Eagle library posted on www.43oh.com forum.
There are two schematic symbols and three footprints:
Full size covers the whole Launchpad footprint